1. Field of the Invention
The invention is directed to an improved overload protection for electric machines such as electric motors and generators.
2. Description of the Prior Art
Electric machines, for example electric motors, frequently contain thermal circuit breakers, which protect the electric machine from destruction or fire in the event that its movement becomes jammed or restricted. Often a suppressor choke is used for this purpose, which is comprised of two parts soldered together at a connecting point, i.e. is comprised of a soldering point, using a solder with a particular melting temperature to form an intentional breaking point. When a carbon brush or a carbon brush cable heats the suppressor choke, this solder is heated and melts at a selected melting temperature. The windings of the suppressor choke exert a certain amount of initial stress on the suppressor choke and therefore on the connecting point so that when the soldering point softens, this connection should be broken. The electric circuit of the electric machine should then be permanently broken and the electric machine should be protected from being destroyed.
Frequently, however, the initial tension is not sufficient to assure a reliable breaking of the soldering point when the suppression choke is heated.